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ch4: better-translation: 扼杀 → 破坏 #102

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ch4: better-translation: 扼杀 → 破坏 #102

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better-translation: 扼杀 → 抹除
Sunt-ing Dec 27, 2020
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better-translation: 扼杀 → 破坏
Sunt-ing Dec 27, 2020
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2 changes: 1 addition & 1 deletion ch4.md
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Expand Up @@ -182,7 +182,7 @@ Thrift CompactProtocol编码在语义上等同于BinaryProtocol，但是如[图4

#### 数据类型和模式演变

如何改变字段的数据类型？这可能是可能的——检查文件的细节——但是有一个风险，值将失去精度或被扼杀。例如，假设你将一个32位的整数变成一个64位的整数。新代码可以轻松读取旧代码写入的数据，因为解析器可以用零填充任何缺失的位。但是，如果旧代码读取由新代码写入的数据，则旧代码仍使用32位变量来保存该值。如果解码的64位值不适合32位，则它将被截断。
如何改变字段的数据类型？这可能是可能的——检查文件的细节——但是有一个风险，值将失去精度或被破坏。例如，假设你将一个32位的整数变成一个64位的整数。新代码可以轻松读取旧代码写入的数据，因为解析器可以用零填充任何缺失的位。但是，如果旧代码读取由新代码写入的数据，则旧代码仍使用32位变量来保存该值。如果解码的64位值不适合32位，则它将被截断。

Protobuf的一个奇怪的细节是，它没有列表或数组数据类型，而是有一个字段的重复标记（这是第三个选项旁边必要和可选）。如[图4-4](img/fig4-4.png)所示，重复字段的编码正如它所说的那样：同一个字段标记只是简单地出现在记录中。这具有很好的效果，可以将可选（单值）字段更改为重复（多值）字段。读取旧数据的新代码会看到一个包含零个或一个元素的列表（取决于该字段是否存在）。读取新数据的旧代码只能看到列表的最后一个元素。

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